Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$107.86	7.245%	$115.6745	$115.67	$115.65	$115.70
Purchase #2	$98.33	11.754%	$109.8877	$109.89	$109.90	$109.90
Purchase #3	$26.64	8.829%	$28.992	$28.99	$29.00	$29.00
Purchase #4	$54.97	13.219%	$62.2365	$62.24	$62.25	$62.20
Purchase #5	$73.52	6.463%	$78.2716	$78.27	$78.25	$78.30
Purchase #6	$96.33	10.652%	$106.5911	$106.59	$106.60	$106.60
Purchase #7	$138.25	7.588%	$148.7404	$148.74	$148.75	$148.70
7 purchase totals =	$595.90		$650.3938	$650.39	$650.40	$650.40